This research projects is designed to investigate the effects of certain abused drugs on human cognitive abilities using both psychological and averaged EEG techniques. Using a modified free recall paradigm, we have found that acute doses of delta 9-THC increase the number of intrusion errors produced during recall. Confidence rating data are now being analyzed to determine whether or not THC also affects the ability to discriminate correct and incorrect responses. Using averaged EEG techniques we have tested subjects on a short-term recognition memory task in both marihuana and placebo conditions. Preliminary results indicate that THC increases overall RT but has no effect on CNV amplitudes. We plan to run additional subjects in this paradigm in a secobarbital-scopolamine-placebo design. We plan to use both averaged EEG and non-EEG tests to investigate the effects of barbiturates and amphetamines on components of attention. We also plan to investigate how these drugs affect the subjective assessment of cognitive performance.